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Valve failure caused by cusp tears in low-profile Ionescu-Shiley bovine pericardial bioprosthetic valves
J
THoRAc CARDIOVASC SURG
1987;93:583-6
Valve failure caused by cusp tears in low-profile Ionescu-Shiley bovine pericardial bioprosthetic valves The pathologic findings in two low-profile Ionescu-Sbiley bioprostheses that failed because of cusp tears are presented. Both valves were in the mitral position, one in place 28 months and the other 40 months. Observation of the valves and their tears suggests that stress at the cusp alignment stitches may be important in the genesis of the tears.
V. M. Walley, M.D., P. Bedard, M.D., M. Brais, M.D., and W. J. Keon, M.D., Ottawa, Ontario, Canada
h e Ionescu-Shiley bovine pericardial bioprosthetic valve has been used at the University of Ottawa Heart Institute for a number of years, and the clinical experience with it has been recently reviewed.I Between April 1977 and October 1984, 637 Ionescu-Shiley valves were inserted including, toward the latter part of this period, 115 "low-profile" Ionescu-Shiley valves (aortic and mitral valves in virtually equal numbers). Previous observations of the mode of primary valve failure in a group of "standard-profile" Ionescu-Shiley valves at the University of Ottawa Heart Institute drew attention to the importance of the cusp alignment stitch as a site of early wear of the cusp, and as a site of eventual cusp tear.' Because the low-profile Ionescu-Shiley valves use an alignment stitch that is modified from that of the standard-profile Ionescu-Shiley valve (information supplied by manufacturer), it is of interest to observe whether this modification alters the pattern of the Ionescu-Shileyvalves' primary failure with tears. Therefore, the pathologic findings in the first two cases at the University of Ottawa Heart Institute of low-profile Ionescu-Shiley valve failure caused by tears are presented. From The University of Ottawa Heart Institute, The Ottawa Civic Hospital, Ottawa, Ontario, Canada. Received for publication March 26, 1986. Accepted for publication April 21, 1986. Address for reprints: V. M. Walley, M.D., Laboratory Medicine, Ottawa CivicHospital, 1053 Carling Ave., Ottawa, Canada KIY 4E9.
Case reports CASE 1. A 56-year-old woman had a history of rheumatic valvulitis and two prior mitral valve replacements. In October 1983, the mitral valve replacement was redone, this time with a No. 33 low-profile lonescu-Shiley bioprosthesis, because of a paraprosthesis leak. In February 1986, the patient came to the hospital with florid pulmonary edema caused by acute mitral valve regurgitation. She had been seen in clinic I week earlier and was entirely well. The patient underwent operation, I day after admission. After 28 months in place, the lonescu-Shiley valve was excised and replaced with a No.3 I Medtronic-Hall mechanical valve. The Ionescu-Shiley valve had a 17 mm cusp tear from stent running down to the cusp base. The free edge of this tear had a small defect near the cusp free margin (Fig. I, A). When the cusp was returned to its original position against the stent, this defect corresponded to the position of the cusp alignment stitch (Fig. I, B). Mild wear of the cusps was seen at two other alignment stitch sites (Fig. 2, A and B). Other findings included moderate endothelialization of the cloth sewing ring on the inflow surfaces, which was associated with some bridging to the cusps and slight limitation of cusp movement as a result (Fig. 3, A). No calcification was demonstrated on radiography. No thrombus or other abnormality was present. CASE 2. A 45-year-old woman had had a previous mitral commissurotomy for rheumatic valvular stenosis. In January 1982, her mitral valve was replaced with a No. 25 low-profile Ionescu-Shiley bioprosthesis. In May 1985, after 40 months in place, the Ionescu-Shiley valve was replaced with a No. 27 Medtronic-Hall mechanical valve. Before this replacement the patient had had a febrile illness, intravascular hemolysis, jaundice, and mitral regurgitation thought to be related to infective endocarditis, but culture results were negative, and she was treated with antibiotics. The Ionescu-Shiley valve had a 5 mm cusp tear from stent
583
The Journal of Thoracic and Cardiovascular
5 8 4 Walley et al.
Surgery
Fig. I. Cusp tears from stent in low-profile lonescu-Shiley mitral bioprostheses. A. Valve from Case I. B. Same valve with cusp reapposed to stent. C. Valve from Case 2. D. Same valve with cusp reapposed to stent. Arrows indicate defects on tear edges that correspond to position of alignment stitches that originally held cusps on their stents. running down from the cusp free margin. There was a small defect on the tear's free edge (Fig. I, C), which corresponded to the position of the cusp alignment stitch when the cusp was returned to its original position (Fig. 1, D). Mild wear of the cusps was seen at two other alignment stitch sites (Fig. 2, C and D). Other examination demonstrated that the inflowcloth sewing ring surfaces had no significant endothelialization, whereas stents and the ventricular sewing ring surfaces had moderate endothelialization and mild limitation of cusp movement as a result (Fig. 3, B). These changes were believed to be
the residua of healed endocarditis. There was minimal calcification of one cusp on radiography. Small amounts of noninfected thrombus were recovered from the ventricular aspects of the cusps but there was no other abnormality.
Discussion To our knowledge, cusps tears in low-profile IonescuShiley bioprostheses have not been previously reported and illustrated. Observations of valves that fail in this
Volume 93 Number 4 April 1987
Valve failure caused by cusp tears 5 8 5
Fig. 2. Areas of mild wear, with cusp swelling and degeneration (black arrows), at cusp alignment stitches. A-B, From Case I. C-D, From Case 2. D. Note that portion of stitch has slipped up to sit on cusp free margin (open arrow).
way are important so that any limitations in valve design may be discovered. The nature of the tears seen in the two cases reported here would suggest that the tears in low-profile Ionescu-Shileyvalves begin at the level of the alignment stitch, the stitch that holds the apposed cusps together and at equal height on each of this valve's three stents. A defect seen in the free edge of each of the tears corresponds to the position of the alignment stitches at the stent apices. The tears apparently propagate toward the cusp base subsequent to their initiation at the free
margin, at the stitches. Areas of mild wear were also observed at other alignment stitches on the same valves. These areas may represent the earliest reaction to mechanical stress at these points and predate more severe degrees of wear and eventual tear. In a group of standard-profile Ionescu-Shiley valves recently reviewed at the University of Ottawa Heart Institute, an observation was made that stress at the alignment stitches or commissural sutures might be implicated in the genesis of many of that valve's tears.'
The Journal of Thoracic and Cardiovascular
5 8 6 Walley et al.
Fig. 3. A, Endothelialization on inflow surface of cloth ring from Case 1, with some bridging to cusp (arrow). B, Endothelialization on ventricular surface of cloth ring from Case 2, with some encroachment on cusp surface (arrow).
In the standard-profile Ionescu-Shiley valves, a spectrum of change from mild to severe wear of cusp at the stitch site, to holes and tears at the site, was observed. The implications of these findings lay in the potential to minimize the numbers of such defects by changes in the valve's design. The low-profile Ionescu-Shiley valve, introduced in 1981, has incorporated design changes
Surgery
that include decrease in the overall valve height, a change in shape of the stents, and a change in the stent material from titanium to Delrin. The alignment stitchcommissural suture was also altered so that a loop over the cusp free margin was substituted for the throughand-through .stitch of the standard-profile IonescuShiley valve (information supplied by manufacturer). The two cases reported here may indicate that stress at the stitch or suture site is still sufficient to produce failure at the site. Although the first case documented above is clearly a primary valve failure caused by tear, interpretation of the second case has to be qualified. In this second case the changes of healed endocarditis contributed to functional abnormalities that precipitated the valve's removal, and it is less clear whether the tear was preexistent, was coexistent, or was contributed to by this infective process. The small number of low-profile Ionescu-Shiley valves that have failed because of tears is perhaps in part a result of their only recent use. The small number does, however, preclude comment on the overall durability of the valve, an issue that will be of considerable importance if more valves fail in this way. This issue aside, the observations made herein contribute to the understanding of how the low-profile IonescuShiley valve fails, and are potentially important in leading to design modifications for improved durability. We acknowledge the help of Debra Toonders in the preparation of this manuscript and Luc Tetreault and Robert Elford in the photography.
REFERENCES
I. Brais MP, Bedard P, Goldstein W, Koshal A, Keon Wl. Ionescu-Shiley pericardiaI xenografts: followup of up to 6 years. Ann Thorac Surg 1985;39: I 05-11. 2. Walley YM, Keon WJ. Patterns of failure in lonescuShiley bovine pericardial bioprosthetic valves. (In press.)
THoRAc CARDIOVASC SURG
1987;93:583-6
Valve failure caused by cusp tears in low-profile Ionescu-Shiley bovine pericardial bioprosthetic valves The pathologic findings in two low-profile Ionescu-Sbiley bioprostheses that failed because of cusp tears are presented. Both valves were in the mitral position, one in place 28 months and the other 40 months. Observation of the valves and their tears suggests that stress at the cusp alignment stitches may be important in the genesis of the tears.
V. M. Walley, M.D., P. Bedard, M.D., M. Brais, M.D., and W. J. Keon, M.D., Ottawa, Ontario, Canada
h e Ionescu-Shiley bovine pericardial bioprosthetic valve has been used at the University of Ottawa Heart Institute for a number of years, and the clinical experience with it has been recently reviewed.I Between April 1977 and October 1984, 637 Ionescu-Shiley valves were inserted including, toward the latter part of this period, 115 "low-profile" Ionescu-Shiley valves (aortic and mitral valves in virtually equal numbers). Previous observations of the mode of primary valve failure in a group of "standard-profile" Ionescu-Shiley valves at the University of Ottawa Heart Institute drew attention to the importance of the cusp alignment stitch as a site of early wear of the cusp, and as a site of eventual cusp tear.' Because the low-profile Ionescu-Shiley valves use an alignment stitch that is modified from that of the standard-profile Ionescu-Shiley valve (information supplied by manufacturer), it is of interest to observe whether this modification alters the pattern of the Ionescu-Shileyvalves' primary failure with tears. Therefore, the pathologic findings in the first two cases at the University of Ottawa Heart Institute of low-profile Ionescu-Shiley valve failure caused by tears are presented. From The University of Ottawa Heart Institute, The Ottawa Civic Hospital, Ottawa, Ontario, Canada. Received for publication March 26, 1986. Accepted for publication April 21, 1986. Address for reprints: V. M. Walley, M.D., Laboratory Medicine, Ottawa CivicHospital, 1053 Carling Ave., Ottawa, Canada KIY 4E9.
Case reports CASE 1. A 56-year-old woman had a history of rheumatic valvulitis and two prior mitral valve replacements. In October 1983, the mitral valve replacement was redone, this time with a No. 33 low-profile lonescu-Shiley bioprosthesis, because of a paraprosthesis leak. In February 1986, the patient came to the hospital with florid pulmonary edema caused by acute mitral valve regurgitation. She had been seen in clinic I week earlier and was entirely well. The patient underwent operation, I day after admission. After 28 months in place, the lonescu-Shiley valve was excised and replaced with a No.3 I Medtronic-Hall mechanical valve. The Ionescu-Shiley valve had a 17 mm cusp tear from stent running down to the cusp base. The free edge of this tear had a small defect near the cusp free margin (Fig. I, A). When the cusp was returned to its original position against the stent, this defect corresponded to the position of the cusp alignment stitch (Fig. I, B). Mild wear of the cusps was seen at two other alignment stitch sites (Fig. 2, A and B). Other findings included moderate endothelialization of the cloth sewing ring on the inflow surfaces, which was associated with some bridging to the cusps and slight limitation of cusp movement as a result (Fig. 3, A). No calcification was demonstrated on radiography. No thrombus or other abnormality was present. CASE 2. A 45-year-old woman had had a previous mitral commissurotomy for rheumatic valvular stenosis. In January 1982, her mitral valve was replaced with a No. 25 low-profile Ionescu-Shiley bioprosthesis. In May 1985, after 40 months in place, the Ionescu-Shiley valve was replaced with a No. 27 Medtronic-Hall mechanical valve. Before this replacement the patient had had a febrile illness, intravascular hemolysis, jaundice, and mitral regurgitation thought to be related to infective endocarditis, but culture results were negative, and she was treated with antibiotics. The Ionescu-Shiley valve had a 5 mm cusp tear from stent
583
The Journal of Thoracic and Cardiovascular
5 8 4 Walley et al.
Surgery
Fig. I. Cusp tears from stent in low-profile lonescu-Shiley mitral bioprostheses. A. Valve from Case I. B. Same valve with cusp reapposed to stent. C. Valve from Case 2. D. Same valve with cusp reapposed to stent. Arrows indicate defects on tear edges that correspond to position of alignment stitches that originally held cusps on their stents. running down from the cusp free margin. There was a small defect on the tear's free edge (Fig. I, C), which corresponded to the position of the cusp alignment stitch when the cusp was returned to its original position (Fig. 1, D). Mild wear of the cusps was seen at two other alignment stitch sites (Fig. 2, C and D). Other examination demonstrated that the inflowcloth sewing ring surfaces had no significant endothelialization, whereas stents and the ventricular sewing ring surfaces had moderate endothelialization and mild limitation of cusp movement as a result (Fig. 3, B). These changes were believed to be
the residua of healed endocarditis. There was minimal calcification of one cusp on radiography. Small amounts of noninfected thrombus were recovered from the ventricular aspects of the cusps but there was no other abnormality.
Discussion To our knowledge, cusps tears in low-profile IonescuShiley bioprostheses have not been previously reported and illustrated. Observations of valves that fail in this
Volume 93 Number 4 April 1987
Valve failure caused by cusp tears 5 8 5
Fig. 2. Areas of mild wear, with cusp swelling and degeneration (black arrows), at cusp alignment stitches. A-B, From Case I. C-D, From Case 2. D. Note that portion of stitch has slipped up to sit on cusp free margin (open arrow).
way are important so that any limitations in valve design may be discovered. The nature of the tears seen in the two cases reported here would suggest that the tears in low-profile Ionescu-Shileyvalves begin at the level of the alignment stitch, the stitch that holds the apposed cusps together and at equal height on each of this valve's three stents. A defect seen in the free edge of each of the tears corresponds to the position of the alignment stitches at the stent apices. The tears apparently propagate toward the cusp base subsequent to their initiation at the free
margin, at the stitches. Areas of mild wear were also observed at other alignment stitches on the same valves. These areas may represent the earliest reaction to mechanical stress at these points and predate more severe degrees of wear and eventual tear. In a group of standard-profile Ionescu-Shiley valves recently reviewed at the University of Ottawa Heart Institute, an observation was made that stress at the alignment stitches or commissural sutures might be implicated in the genesis of many of that valve's tears.'
The Journal of Thoracic and Cardiovascular
5 8 6 Walley et al.
Fig. 3. A, Endothelialization on inflow surface of cloth ring from Case 1, with some bridging to cusp (arrow). B, Endothelialization on ventricular surface of cloth ring from Case 2, with some encroachment on cusp surface (arrow).
In the standard-profile Ionescu-Shiley valves, a spectrum of change from mild to severe wear of cusp at the stitch site, to holes and tears at the site, was observed. The implications of these findings lay in the potential to minimize the numbers of such defects by changes in the valve's design. The low-profile Ionescu-Shiley valve, introduced in 1981, has incorporated design changes
Surgery
that include decrease in the overall valve height, a change in shape of the stents, and a change in the stent material from titanium to Delrin. The alignment stitchcommissural suture was also altered so that a loop over the cusp free margin was substituted for the throughand-through .stitch of the standard-profile IonescuShiley valve (information supplied by manufacturer). The two cases reported here may indicate that stress at the stitch or suture site is still sufficient to produce failure at the site. Although the first case documented above is clearly a primary valve failure caused by tear, interpretation of the second case has to be qualified. In this second case the changes of healed endocarditis contributed to functional abnormalities that precipitated the valve's removal, and it is less clear whether the tear was preexistent, was coexistent, or was contributed to by this infective process. The small number of low-profile Ionescu-Shiley valves that have failed because of tears is perhaps in part a result of their only recent use. The small number does, however, preclude comment on the overall durability of the valve, an issue that will be of considerable importance if more valves fail in this way. This issue aside, the observations made herein contribute to the understanding of how the low-profile IonescuShiley valve fails, and are potentially important in leading to design modifications for improved durability. We acknowledge the help of Debra Toonders in the preparation of this manuscript and Luc Tetreault and Robert Elford in the photography.
REFERENCES
I. Brais MP, Bedard P, Goldstein W, Koshal A, Keon Wl. Ionescu-Shiley pericardiaI xenografts: followup of up to 6 years. Ann Thorac Surg 1985;39: I 05-11. 2. Walley YM, Keon WJ. Patterns of failure in lonescuShiley bovine pericardial bioprosthetic valves. (In press.)